She did it...the other way!!
When Neil and I heard Mary awake this morning he got up and went in to get her. When he carried her back into our room and put her on the bed he said, "she was just playing on her back." Imagine my surprise, because I remembered putting her down on her belly last night. I raised my head and said,
Me: "Are you serious?"
Neil: "Is that a big deal?"
Me: "Have you seen her do it before?"
Neil: "No"
So, I explained to him that babies rolling from their backs to their belly is the first big deal and when they learn how to roll back it is another big deal. Apparently, Mary can do it now!! Yay sweet baby - you're getting so strong!